Magnetic latch relay



P 1969 1 :w; J. RICHERT v 3 470 MAGNETIC LATCH RELAY Filed Nov. 7. 196'? FIG. 2

29 l I INVENTOR. WALTER J. RI ERT mm I M AGENT United States Patent 3,470,510 MAGNETIC LATCH RELAY Walter J. Richert, Princeton, lnd., assignor to American Machine & Foundry Company, a corporation of New Jersey Filed Nov. 7, 1967, Ser. No. 681,233 Int. 'Cl. H011? 7/08 US. Cl. 335-230 11 Claims ABSTRACT OF THE DISCLOSURE A clapper type relay with the clapper armature spring biased to its reset position, the relay frame including a permanent magnet unaffected by energization of the electromagnet, and an electromagnet energized to set the relay and having a core with remanent characteristics which with the frame magnet latches the relay in its set condition when the electromagnet is de-energized.

granted Oct. 4, 1960, to me. However, magnetic latch features heretofore have been unsatisfactory in clapper type relays. Such relays could not tolerate fluctuations in coil energization and are subject to false latching when the relay was reset because of swamping of the latch magnet. Also, precise manufacturing tolerances and matching of relays to their applications heretofore were required.

Accordingly, an object of the present invention is to provide a reliable clapper type relay with a magnetic latch that is of rugged construction, relatively inexpensive to manufacture and can tolerate varying and severe operating conditions.

Another object of the present invention is to provide the foregoing relay in which the latch magnet is substantially immune from swamping by the coil field of the electromagnet.

And another object of the present invention is to provide the foregoing relay in which minimum operating energization provides suflicient magnetic force after coil de-energization to maintain the magnetic latching condition under severe environmental conditions until the relay is reset.

The present invention contemplates a clapper type relay comprising first and second magnet means and a separate magnetic circuit for the flux of each of said magnet means; a working air gap common to both said separate circuits; another magnetic circuit common to said first and second magnet means for opposing flux therefrom when flux across said air gap from said first and second magnet means is in the same direction, and for flux in the same direction therefrom when there is opposing flux across said air gap; a clapper type armature controlling said air gap and being pivotable at one end thereof in response to flux across said air gap when electromagnetic flux is provided and betweenone position closing said air gap when the flux across said air gap is in the same direction and another position opening said air gap when there is opposing flux across said air gap; electromagnet means adapted to be energized for orienting said first magnet means to control the direction of the flux thereof and for providing electromagnetic fiux across said air gap with the flux of said first magnet means in the same direction across said air gap as the flux of said second magnet means, and to be reversely energized to cause the electromagnetic flux with the flux of said first magnet means across said air gap to oppose the flux of said second magnet means; and said first and second magnet means providing opposing flux across said air gap when said electromagnetic means is de-energized after reverse energization, and to provide flux in the same direction when said electromagnetic means is de-energized after energization to magnetically latch the armature and maintain the closed gap until said electromagnetic means is reversely energized.

The foregoing and other objects and advantages will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein several embodiments of the invention are illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration purposes only and are not to be construed as defining the limits of the invention.

FIGURE 1 is a side elevational view of a relay made in accordance with the present invention;

FIGURES 2 and 3 are enlarged side elevational views of the frame, core armature and spring means of the relay of FIGURE 1 diagrammatically illustrating the various flux paths thereof when it is in the reset and set conditions, respectively; and

FIGURES 4 and 5 are fragmentary side elevational views with portions thereof broken away to show relay construction details in accordance with the present invention.

Referring now to the drawings and particularly to FIG- URE 1, a relay made in accordance with the present invention is provided with a generally C-shaped support means or frame 10 having a base member 11, a bracket member 14 and a permanent magnet 16 to provide magnet means there between. The members 11 and 14, which are of magnetic material, are spaced from and substantially parallel to each other. Base member 11 has at one end an armature supporting leg 12 which extends upwardly past member 14, and at its other end connecting means which, in this instance, is an upwardly extending leg or flange 13. Bracket member 14 has at one end a leg 15 which depends toward the base member 11.

Legs 12 and 15 are spaced from and substantially parallel to each other. The permanent magnet 16 is disposed in the space between and connected to the legs 12 and 15, thereby connecting the base and bracket members 11 and 14 together. Therefore, frame 10 has a permanent magnet means disposed between two end portions of magnetic material.

To complete the general frame structure, an armature retainer member 17 is connected to the side of leg 12 opposite from the magnet 16. The lower end of retainer 17 is provided with a projection 18, which extends there from in a direction away from magnet 16, for retaining one end of a tail spring 19 as shown.

The novel relay is provided with an actuating means or electromagnet 20 having a coil 21 and a core 22 which is connected at one end to the base member 11 and extends therefrom through the coil 21 and bracket member 14. The bracket member 14 supports the other end of core 22 which provides an exposed end face or surface 23. Core 22 also is provided with magnet means which, in this instance, is an intermediate permanent magnet layer 24 disposed between two end portions of magnetic material.

Thus, while frame 10 and core 22 may differ from each other as to size, shape and material, they are similar to each other as to function because each has a permanent magnet between two end portions of magnetic material which provides .a predetermined flux to the various fiux paths of the relay when the coil 21 is de-energized. The definition of permanent magnet as used herein in connection with frame magnet 16 and core magnet 24 is intended to be in accordance with the broad definition thereof as set forth in lines 12 to 14 of column 2 on page 1683 of Websters Third New International Dictionary, Unabridged, 1961, wherein a permanent magnet is a magnet which retains its magnetism after removal of the magnetizing force.

The permanent magnet 16 together with legs 12 and .are disposed on one side of the electromagnet 20 while a terminal header or block is provided on the other side thereof and is connected to the flange 13 in any suitable manner well known in the art. The header 25 supports at least one pair of fixed contacts 26 and 27 which are spaced from each other and have terminal connection portions. The coil 21 is considered to be of simple construction wherein a single extent of wire is used for the coil windings and a pair of terminals 28 and 29, which are fixedly supported by the header 25, are provided for the wound wire. Coil 21 may be of complex construction having two separate sets of windings, as will be further discussed. If coil 21 is of complex construction, a second pair of terminals 28 and 29 would be required.

The armature, its pivotal support and the tail spring arrangement, as shown in FIGURE 1 and which will be described briefly herein, is for illustration purpose only and is not intended to define the limits of the present invention. A relay construction corresponding to this illustrative combination of parts is shown, described and claimed in US. Patent 3,201,541 granted Aug. 17, 1965, to me and assigned to the same assignee as is the present application. It should be further understood that recitation of the armature of magnetic material is to be construed in its broadest sense to include a non-magnetic armature with a plate or layer of magnetic material as is required in the exemplar relay illustrated and described herein.

An armature 30 of magnetic material is pivotally supported .at one end on the free end of leg 12 opposite from the base member 11. Armature 10 extends from its supported end toward header 25 and terminates in a free end which overlies the exposed end surface 23 of core 22. A pair of tails or tail portions 31 (only one shown) and a projection 32 spaced between the tails extend from the supported end of the armature 30 in a direction away from core 22. The tails 31 are then bent or angled relative to the major plane of the armature 30 and terminate in free ends which may abut leg 12 to limit the maximum pivotal displacement of the armature 30 from the core face 23 which is in a counterclockwise direction as viewed in FIGURE 1. Tail spring 19 which is retained at one end by projeciion 18 of the retainer 17, is retained at its other end by the armature projection 32 and thereby is maintained under tension for biasing the armature 30 to pivot away from the exposed core end face 23.

A movable contact is provided to cooperate with each pair of fixed contacts 26 and 27 to accomplish the relay switch operation. The contacts are not specific to the present invention. Therefore, only one pair of fixed contacts 26 and 27 with an associated movable contact 36- 37 will be considered to facilitate description. An insulated block means 33 is connected to the armature 30 for mounting the spring arm 34 of a movable contact. One end of arm 34 extends from the mounting means 33 and away from header 25 to provide .a connection terminal 35. Arm 34 also extends axially toward header 25 terminating in a free end disposed between fixed contacts 26 and 27. A pair of contact faces 36 and 37 are connected to opposite sides of the free end of spring contact arm 34 to provide the requisite movable contact, and are so arranged that contact face 36 engages contact 26 when the relay is open or reset and face 37 engages contact 27 when the relay is closed or set.

It should readily be understood that there are substantially three sources of flux, namely, the two permanent magnet means 16 and 24, and the electromagnet 20. Orientation of each flux source if it were considered by itself in the absence of such other sources would be unimportant. However, for proper relay operation or response the interaction of the magnetic forces derived from all such sources must be considered which necessitates orientation of each of the magnetic sources relative to the others, as will now be discussed.

Referring now to FIGURE 2, the relay is considered as being open or reset prior to operation with the north pole of the permanent frame magnet 16 adjacent leg 15, and the north pole of the permanent core magnet 24 adjacent the lower portion of magnetic material of core 22. A single closed flux path 40 and two variable reluctance flux paths 41 and 42 are indicated in FIGURE 2,. with arrowheads denoting the direction of flux in each of the paths when permanent magnets 16 and 24 are polarized as above and the electromagnet 20 is de-energized. A working air gap 39 is formed between the armature 30 and the exposed core end face 23, and is included in each of the flux paths 41 and 42.

The polarity of the permanent frame magnet 16 does not change during operation of the relay, and the direction of the resulting flux provided thereby to each of the paths 40 and 41 is always in the direction as indicated in FIGURE 2. The direction of flux derived from the permanent core magnet 24 when polarized as discussed above is provided to each of the flux paths 40 and 42 in the direction of the arrowheads, as indicated also in FIGURE 2. Therefore, in the initial quiescent open state of the relay or when the relay is reset as depicted in FIGURE 2, the flux derived from permanent magnets 16 and 24 in reluctance paths 41 and 42, respectively, buck or oppose each other and the formed air gap 39 across these flux paths is at its maximum. However, the flux derived from the magnets 16 and 24 are coincident in the closed flux path 40. Therefore, the magnetic force across the working or formed air gap 39 is insufficient to move the armature 30 which is retained away from the exposed core end face 23 by the bias of tail spring 19.

To close or operate the relay, the coil 21 of the electromagnet is energized which substantially simultaneously reverses the polarity of the permanent magnet 24 and establishes the corresponding polarity of core 22. This results, as indicated in FIGURE 3, in reversing the flux derived from the magnet 24 which with the electromagnetic flux opposes the flux provided to the common flux path 40 from the permanent frame magnet 16. At this time, the common flux path 40 appears to have a much higher reluctance than the flux paths 41 and 42. The flux now provided to both reluctance paths 41 and 42 which is derived from all three sources is in the same direction across the air gap 39. To reiterate, the direction of the flux provided to flux paths 40 and 41 by the frame magnet 16 is not effected by energization of the coil 21. As a result of the apparently high reluctance of path 40 substantially all the flux is shunted therefrom and a working magnetic force is established across the air gap 39 which causes the armature 30 to pivot against the force of spring 19 and into contact with the exposed core end face 23. The working air gap 39 is now substantially closed and reluctance of the flux paths 41 and 42 is minimal.

The electrical energy or energy pulse applied to coil 21 for operating the relay may be of minimum duration and intensity necessary to reverse the polarity of the permanent core magnet 24 and to provide an electromagnetic flux required in addition to the flux derived from permanent magnets 16 and 24 for establishing the necessary working magnetic force across the air gap 39. It should be understood that the energization of coil 21 could greatly exceed the minimum parameters set for any particular relay with no detrimental effects on the relay or its operation. This simplifies production and permits increased manufacturing tolerances.

De-energization of coil 21 is attended by termination of the elemtromagnetic flux. The polarity of the permanent core magnet 24 remains as established by coil energization and the flux which appears as remanent flux from the permanent magnets 16 and 24 remains unchanged as to direction as indicated in FIGURE 3, and is effective to magnetically latch the relay or clamp the armature 30 in its closed position. It should be understood that when the reluctance of the common flux path 40 appears high, there may be some leakage flux as is indicated in FIG- URE 3.

To reopen or reset the latched or set relay, reverse electrical energy is applied to coil 21 causing the polarity of the permanent core magnet 24 to reverse and substantially simultaneously to establish the corresponding polarity of the core 22. As a result, the flux derived from magnet 24 reverses and with the electromagnetic flux provided to reluctance path 42 now opposes the flux provided to reluctance path 41 derived from the permanent frame magnet 16 and causes the armature 30 to drop out or move away from core face 23 under the bias of spring 19. At this time, the flux provided to the closed path 40 from all three sources is coincident in direction.

It has been found that drop out, release, opening or resetting of the relay can be accomplished by a field energy which is equal to a relatively small portion of magnetic latching energy. However, it is not necessary to limit the field energy to such relatively small proportions. In some instances, it was noted, the release energy may be increased as much as twenty times that required for release before the flux derived from the permanent core magnet 24 and the electromagnetic flux will overcome the bucking flux derived from the permanent frame magnet 16 and cause false operation to occur. This again facilitates production of this type of relay, and permits increased manufacturing tolerances and broader application of relays of this type than was heretofore possible.

It should be realized that while in most instances it may be preferred to reverse the flux of the core magnet means 24, for reset, and provide a relatively weak tail spring 19 merely for moving and retaining the armature 30 away from the core face 23, this invention is not limited thereto. The broad concept of the present invention is to control all of the forces acting on armature 30 by controlling the direction and magnitude of flux across the working air gap 39 to operate the relay and to attain magnetic latching.

Accordingly, a substantially strong tail spring 19 may be employed, and to set the relay the coil 21 of the electromagnet 20 would be sufiiciently energized to provide adequate flux through magnet means 24 and the electromagnet 20 which together with the flux from magnet means 16 establishes a working magnetic force across the working gap 39 to overcome the bias of tail spring 19. The flux from magnet means 16 and 24 also must, when the coil 21 is de-energized, be capable of overcoming the bias of spring 19 for latching.

Under these conditions, reversal of the flux of magnet means 24 would not be necessary in all instances. Therefore, by reversely energizing the coil 21 for reset, electromagnetic flux would be provided to flux path 42 in the direction opposite to the direction indicated in FIGURE 3. The field derived by such reverse energization would be limited, as desired, so the polarity of the magnet means 24 is not reversed but the density of the flux therefrom is substantially reduced.

The tail spring 19, in this instance, would be specified for providing a force biasing armature away from the core face 23 which exceeds the resulting opposing magnetic force derived from the flux which includes the lower density flux of magnet means 24.

Operation or relay closing in response to release energization of coil 21 is false operation and is an unstable condition. It should be readily understood that removal of release energization from coil 21 will cause termination of the electromagnetic flux. The relay will have been returned to its initial quiescent open state or reset condition with bucking fiuX being provided to the reluctance paths 41 and 42 by the frame magnet 16 and the core magnet 24, respectively.

The stable operating characteristics and elimination of critical parameters as discussed are made possible by use of the permanent frame magnet 16 which is immune to reversing by the coil field of the electromagnet 20, and the auxiliary magnetic circuit 41 associated with the frame magnet which combine to provide the requisite bucking effects.

A relay made in accordance with the present invention can tolerate large fluctuations in the level of coil energization, normally rigid tolerances are obviate-d in the manufacture of the coil thereof, and the electrical parameters governing the application or use of such relays are substantially less restrictive than those heretofore encountered. Although a permanent magnet is provided in each the frame and the core construction, each permanent magnet is normally of a material different from that of the other. However, there is no intent to limit the present invention to the embodiment of an electromagnet having a core construction involving a permanent magnet portion.

As previously discussed, when the orientation or polarity of core magnet 24 reverses, the direction of the flux derived therefrom is reversed. It also should be understood that core magnet 24 is subject to coil energization. Therefore, the polarity of the core magnet 24 will normally correspond to the instantaneous polarity of the core 22 when the coil 21 is sufliciently energized to either set or reset the relay.

Upon energization of coil 21, the resulting flux appears to flux paths 40 and 42 as being from a single source and has a unit density substantially equal to the density of the flux derived from manget 24 combined with the electromagnetic flux density. Upon coil de-energization, only the flux from the core magnet 24 remains and has a density which is substantially lower than the unit density during coil energization. It should be readily understood that the flux from magnet 24, in effect, appears as a remanent flux. Accordingly, the electromagnet 20 alternatively may be provided with a unitary core piece of remanent magnetic material. Upon coil energization the resulting flux density would substantially correspond to the unit density heretofore discussed, and upon subsequent de-energization a remanent flux would be realized of a density substantially equal to that realized by use of the core magnet 24.

As shown in FIGURE 4, the permanent frame magnet 16 may be connected between legs 12 and 15 of frame 10 by one or more non-magnetic rivets 16A. Alternatively, the contacting surfaces of magnet 16 and frame legs 12 and 15 can be joined by adhesives, brazing or any other known method which is compatible with the magnet and frame material chosen for a particular relay made in accordance with the present invention.

Similarly, core 22 can be made in various ways. The permanent magnet may be brazed to the end portions of core 22 or, as shown in FIGURE 5, a pin 24A may extend through the magnet 24 and the ends thereof pressfitted into aligned blind openings in the top and bottom portions of core 22. Alternatively, the two portions of core 22 and the intermediate magnet 24 may be retained within the tubular body 22A of the bobbin of the electromagnet 20 or a separate non-magnetic thin wall tube. As previously sta ted, since the flux of the permanent core magnet 24 appears to the flux circuits as a remanent flux, the core 22 may be made of a single piece or in part of any suitable remanent magnetic material.

The core material required to provide flux with the flux of frame magnet 16 when coil 21 is de-energized will be determined primarily by its magnetic parameters and then possibly by the application environment of the relay.

Although several embodiments of the invention have been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes may also be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

I claim:

1. In a clapper type relay,

first and second magnet means and a separate magnetic circuit for the flux of each of said magnet means;

an air gap common to both said separate circuits;

a closed magnetic circuit common to said first and second magnet means appearing as a high reluctance flux path when flux across said air gap from said first and second magnet means is in the same direction, and a shunt for flux in the same direction therefrom when there is opposing flux across said air gap;

a clapper type armature controlling said air gap and being pivotable at one end thereof in response to flux across said air gap when electromagnetic flux is provided and between one position wherein said air gap is open and another position wherein said air gap is closed;

means biasing said armature to the said one position;

electromagnet means adapted to be energized for orienting said first magnet means thereby controlling the direction and density of the flwr thereof and for providing electromagnetic flux across said air gap with the flux of said first magnet means in the same direction across said air gap as the flux of said second magnet means to cause said armature to pivot to the said one position and to be reversely energized to reverse the electromagnetic flux and to change the flux of said first magnet means by reorientation so the flux across said air gap including the flux of said second magnet means provides a magnetic force less than the bias on said armature; and

said first and second magnet means providing flux resulting in a magnetic force across said air gap when said electromagnetic means is de-energized after reverse energization which is less than the bias on said armature and to provide flux in the same direction when said electromagnetic means is de-energized after energization to magnetically latch the armature and maintain the closed gap until said electromagnetic means is reversely energized.

2. The relay in accordance with claim 1, wherein:

said first magnet means and said electromagnet means when energized both provide flux to the magnetic circuit for the flux of said first magnet means and across said air gap; and

said first magnet means continuing to provide flux to such circuit and across said air gap when said electromagnet means is de-energized which appears as a remanent flux of said electromagnetic means.

3. The relay in accordance with claim 1, wherein:

reverse energization of said electromagnet means acts on said first magnet means to cause reversal of the flux therefrom.

4. The relay in accordance with claim 1, wherein:

reverse energization of said electromagnet means acts on said first magnet means to reduce the density of the flux therefrom below a required minimum.

5. The relay in accordance with claim 2, wherein:

said second magnet means is sufliciently isolated from said electromagnetic means to prevent the field of said electromagnetic means when energized from effecting the magnetic orientation of said second magnet means. 6. The relay in accordance with claim 1, further comprising a frame of magnetic material, and

said second magnet means being connected to said frame between two portions thereof;

said electromagnetic means being connected to said frame, and providing a coil to be energized and a core of magnetic material having an exposed end face;

said first magnet means forming at least a part of said core;

said armature being mounted on said frame at said one end at which it pivots and being free at its other end which extends across said core;

said free end of said armature and said exposed end face of said core defining said air gap;

said armature being at least in part of magnetic material engaging said frame at said one of said armature connected to said frame and in contact with said exposed face of said core when said air gap is closed; and

said frame and core providing said closed magnetic circuit and with said armature providing said separate magnetic circuits.

7. The relay in accordance with claim 6, wherein:

said frame is comprised of two frame members of magnetic material each having a leg portion disposed substantially parallel to and spaced from the leg portion of the other;

said second magnet means being a permanent magnet disposed between and connected to said leg portions;

one of said frame members engaging said core adjacent the exposed face thereof and the other of said frame members being connected to the end of the core opposite from said exposed face; and

said leg portion of said other of said frame members being connected to and supporting said armature.

8. The relay in accordance with claim 6, wherein:

said first magnet means is a permanent magnet which forms a part of said core of said electromagnet means.

9. The relay in accordance with claim 8, wherein:

said core has a pair of end portions of magnetic material; and

said permanent magnet is disposed between said end portions.

10. The relay in accordance with claim 6, wherein:

said first magnet means is of a remanent magnet material.

11. The relay in accordance with claim 10, wherein:

said core has a pair of end portions of magnetic mate rial; and

said remanent magnet is disposed between said end portions.

References Cited UNITED STATES PATENTS 2,869,050 1/1959 Van Urk et a1. 335229 3,317,871 5/1967 Adams 335230 3,349,356 10/1967 Shinohara 335254 G. HARRIS, Primary Examiner US. Cl. X.R. 

